Branch circuits in Subpanels [RE-wrenches]

[Jeff Clearwater]

<x-flowed>

Hey Ray,

Won't any effects that do exist from inductive "eddy currents" or 
such  cancel because he'll also have a single large neutral conductor 
through the nipple too?

AndI thought inductive current problems were only significant with DC.

And If they are stacked inverters (120/240) so that there are 
currents of both legs - then those would cancel as well no?

Hope that helps!

Jeff C.



>Ray,
>
>The issue with passing only the line conductors through the conduit nipple
>between panels is induced eddy currents within the conduit nipple. The
>changing magnetic field(s) in the conductor(s) passing through the conduit
>nipple induces an electric current within the surrounding metallic conduit.
>If both line and neutral of the given circuit pass through the conduit, then
>the opposite effects of each wire's changing magnetic fields cancel one
>another out, and there is no net effect on the surrounding conduit. This is
>why all current carrying conductors of a particular circuit must remain
>together inside metallic raceways. The problem is, the induced eddy currents
>in the surrounding conduit can result in the conduit heating up, which I
>believe is due to the conduit material's internal resistance to these eddy
>currents, which can be rather high. I am sure that there are engineering
>calcs that can be performed to ascertain how significant this heating effect
>may be based upon the wire size, AC frequency, amperage, conduit size,
>material type, length, phase of the moon and which side you part your hair
>on.
>
>I'm not sure how you feel about them, but there are new connectors that take
>the place of wire nuts. Similar to "backstab" push-in connections to AC
>light switches and receptacles, these connectors are small-ish blocks that
>you push the stripped ends of solid conductor wire into. I think these
>connectors can be purchased with different numbers of holes to accept two to
>several conductors. They may help you to save room in the primary load
>center as you splice on extensions. I've not used them in place of wire
>nuts, and I never back stab receptacles when wiring AC circuits, so I can't
>vouch for this approach, but it may be worth considering. It's an
>alternative to crimp butt splices, and these connectors are listed for this
>type of purpose anyway...
>
>I hope that helps.
>
>Dan Rice
>Abundant Sun, LLC
>
>----- Original Message -----
>From: "Ray Walters" <walters at taosnet.com>
>To: <RE-wrenches at topica.com>
>Sent: Friday, October 20, 2006 6:54 PM
>Subject: Branch circuits in Subpanels [RE-wrenches]
>
>
>|
>| Hi All;
>|
>| I have a question related to the grid/tie back up question. When we add
>| a sub panel for circuits to be powered by the inverter, we install a
>| short 1" to 3 " by 2 " diam nipple to connect the sub panel to the
>| existing load center. In many cases the existing branch circuit wiring
>| is too short to run directly over to the sub panel, so we wire nut
>| extensions to make the run over to the new sub panel. To avoid too many
>| wire nutted connections, we have considered just running the hots over
>| to the adjacent sub panel, and leave the neutrals and grounds connected
>| (as before) to the existing main load center. We run #6 or #4 over to
>| connect the subpanel's ground and nuetral bars to the main load center.
>| (yes, we observe the "nuetral bonded to ground in only one place" rule)
>| Now, I realise code specifies that hots, neutrals, and grounds on branch
>| circuits have to be run in the same raceway, and I wouldn't consider
>| this, if the load centers were not side by side. What are the potential
>| problems here? Basically we're trying to observe another section of the
>| code that specifies "professional, workmanship like manner": and wire
>| nutting all the hots, neutrals, and grounds to jump 2 ft over to an
>| adjacent box looks like a real mess, not to mention the potential
>| dangers of all those extra connections crammed into the sides of the
>| existing load center.
>| Obviously, if its new construction, we can get the branch wires left
>| long enough to do this right. However, this is an existing service
>| situation. What do you all think or do in these situations? (I've also
>| considered crimped butt splices, but IMHO, they are not reliable on
>| solid core wire.)
>|
>| Thanks very much,
>|
>| Ray Walters
>
>
>- - - -
>To send a message: RE-wrenches at topica.com
>
>Archive of previous messages: http://lists.topica.com/lists/RE-wrenches/read
>
>List rules & how to change your email address: 
>www.mrsharkey.com/wrenches/etiquette.php
>
>Check out participant bios: www.mrsharkey.com/wrenches/
>
>Hosted by Home Power magazine
>
>Moderator: michael.welch at homepower.com


-- 
~~~~~~~~~~~~~
Jeff Clearwater
Village Power Design
Sustainable Energy & Water Solutions for Home & Village
http://www.villagepower.com
gosolar at villagepower.com
NABCEP (tm) Certified Solar PV Installer

530-470-9166
877-SOLARVillage
877-765-2784
65 Schoolhouse Rd
Amherst, MA 01002
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~`~


- - - -
To send a message: RE-wrenches at topica.com

Archive of previous messages: http://lists.topica.com/lists/RE-wrenches/read

List rules & how to change your email address: www.mrsharkey.com/wrenches/etiquette.php

Check out participant bios: www.mrsharkey.com/wrenches/

Hosted by Home Power magazine

Moderator: michael.welch at homepower.com
--^----------------------------------------------------------------
This email was sent to: michael.welch at homepower.com

EASY UNSUBSCRIBE click here: http://topica.com/u/?bz8Qcs.bz9JC9.bWljaGFl
Or send an email to: RE-wrenches-unsubscribe at topica.com

For Topica's complete suite of email marketing solutions visit:
http://www.topica.com/?p=TEXFOOTER
--^----------------------------------------------------------------


</x-flowed>